Tandem Forster Resonance Energy Transfer Induced Luminescent Ratiometric Thermometry in Dye-Encapsulated Biological Metal-Organic Frameworks

Luminescent ratiometric thermometers (LRTs) based on the emission intensity ratio with self-reference functions guarantee a temperature sensing of fast response, high precision, and excellent spatial resolution. For monitoring temperature at the cellular level, the use of metal-organic frameworks (MOFs) as probes, especially biocompatible ones, is still in its nascency. By employing a biological MOF, Zn-3(benzene-1,3,5-tricarboxyl)(2)(adenine)(H2O) (ZnBTCA), as a host and thermosensitive fluorescent dyes as guests, a series of dye@ZnBTCA is synthesized and studied as potential LRT materials, featuring a unique mechanism of tandem Forster resonance energy transfer among the MOF host and the multiple dye guests. This scenario is significantly different from the commonly reported lanthanide or mixed-lanthanide MOFs where energy transfer occurs between lanthanide ions. Acf-RB@ZnBTCA, in particular, not only exhibits highly efficient ratiometric temperature-sensing properties under physiological cellular conditions but also can be excited under visible light.